US5046583A - Oil level sensor for an internal combustion engine - Google Patents

Oil level sensor for an internal combustion engine Download PDF

Info

Publication number
US5046583A
US5046583A US07/528,036 US52803690A US5046583A US 5046583 A US5046583 A US 5046583A US 52803690 A US52803690 A US 52803690A US 5046583 A US5046583 A US 5046583A
Authority
US
United States
Prior art keywords
oil
inner electrode
oil level
sensor body
sensor
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US07/528,036
Inventor
Asao Sasaki
Yosuke Kubota
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Subaru Corp
Original Assignee
Fuji Jukogyo KK
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Fuji Jukogyo KK filed Critical Fuji Jukogyo KK
Assigned to FUJI JUKOGYO KABUSHIKI KAISHA, 7-2 NISHISHINJUKU 1-CHOME, SHINJUKU-KU, TOKYO, JAPAN A CORP. OF JAPAN reassignment FUJI JUKOGYO KABUSHIKI KAISHA, 7-2 NISHISHINJUKU 1-CHOME, SHINJUKU-KU, TOKYO, JAPAN A CORP. OF JAPAN ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: KUBOTA, YOSUKE, SASAKI, ASAO
Application granted granted Critical
Publication of US5046583A publication Critical patent/US5046583A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
    • G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
    • G01F23/24—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of resistance of resistors due to contact with conductor fluid
    • G01F23/241—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of resistance of resistors due to contact with conductor fluid for discrete levels
    • G01F23/243—Schematic arrangements of probes combined with measuring circuits
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
    • G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
    • G01F23/24—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of resistance of resistors due to contact with conductor fluid
    • G01F23/241—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of resistance of resistors due to contact with conductor fluid for discrete levels
    • G01F23/242—Mounting arrangements for electrodes

Definitions

  • the present invention relates to an oil level sensor for detecting the level of lubricating oil in an internal combustion engine.
  • an oil level sensor is provided for monitoring the level of the lubricating oil at all times.
  • the oil sensor detects a lower level for the oil lower than a set level, the engine is stopped or an alarm lamp is turned on to prevent the engine from being damaged.
  • Japanese Patent Applications Laid-Open 62-93417 and 62-26379 disclose oil sensors employed with an oil pressure switch and a reed switch, respectively.
  • the oil sensor employed with the reed switch consists of various components such as a float and a magnet in addition to the reed switch, so that the oil sensor is complicated in construction. Further, the sensor must be assembled in a crankcase before assembling the engine.
  • the oil sensor employed with the oil pressure switch can not be used for an engine without an oil pump.
  • a fluid sensor detects the amount of fluid by measuring a resistance of the fluid.
  • the fluid sensor comprises a center electrode and an outer electrode surrounding the center electrode at a predetermined distance.
  • the fluid sensor detects the volume and concentration of the fluid, and other conditions in accordance with the variation of the resistance between the center electrode and the outer electrode.
  • the variation of the resistance is detected by measuring a current flowing in the fluid sensor.
  • the current representing the variation of the resistance of oil is very small, because the resistance is large.
  • a shielded wire must be employed for a signal line in order to prevent the influence of noises.
  • the shielded wire must be connected to a control unit by a connector, which causes an increase of parts and the assembling process.
  • a high-insulating resistor must be provided in the control unit.
  • the high-insulating resistor electrically affects other circuits.
  • the object of the present invention is to provide an oil level sensor which detects the level of oil in an oil pan with accuracy without influence of noise.
  • Another object of the present invention is to provide an oil level sensor in which the number of the parts of the sensor is reduced, thereby reducing the manufacturing cost and the assembling process.
  • an oil level sensor comprising a cylindrical hollow sensor body made of conductive resin, an inner electrode guide made of an insulator and secured to an inner wall of the sensor body, an elongated inner electrode made of conductive resin and securely mounted in the inner electrode guide so as to keep a predetermined distance from the inner wall of the sensor body, and an oil level detector circuit provided in the sensor body and electrically connected between the inner electrode and the sensor body.
  • the inner electrode has a flange at a base portion thereof and a connecting portion projected from the flange, and a circuit board is secured to the connecting portion.
  • An oil level detector circuit has a comparator for producing an output signal having a logical level and a thermistor for compensating the resistance variation of oil caused by heat.
  • FIG. 1 is a schematic illustration of an oil level sensor according to the present invention, a part of which is shown in section;
  • FIG. 2 is a sectional view showing the oil level sensor
  • FIG. 3 is a sectional view of the oil level sensor taken along the line III--III of FIG. 2;
  • FIG. 4 is a circuit of an oil level detector
  • FIG. 5 is a graph showing characteristic of insulation resistance and temperature of oil.
  • an oil level sensor A is provided in an oil pan 19 of an engine (not shown) by engaging a threaded opening 19a formed in the oil pan through a packing 20.
  • the oil sensor A has a cylindrical sensor body 1 served as an outer electrode, which is made of electrically conductive resin including carbon particles molded by injection molding.
  • the sensor body 1 comprises a screw head 1a, a flange 1b adjacent to the screw head 1a, and an outer thread 1c adjacent to the flange 1b.
  • the sensor body 1 has a cylindrical hollow portion 1e and air vents 1f formed in the body, communicating with the hollow portion 1e.
  • a stepwise portion 1g is formed on an inside wall of the sensor body 1.
  • an inner electrode guide 2 is securely mounted in the hollow portion 1e.
  • the guide 2 is made of high-resistance insulation resin with heat proof.
  • the guide 2 has a shoulder portion 2a engaged with the stepwise portion 1g of the sensor body 1, a cylindrical body portion 2a' and a taper portion 2c formed on an end of the cylindrical portion 2a'.
  • the guide 2 has an axial hole formed along the axis, opening at both ends.
  • An annular groove 2b is formed on the cylindrical body portion 2a' for engaging an O-ring 3a.
  • the entire outer surface of the guide 2 or at least an outer surface of the taper portion 2c is coated with such material as fluororesin having heat proof, electrical resistivity and oil repelling characteristics for preventing the oil from adhering to the guide 2.
  • the guide 2 has a recess 2d formed on the shoulder portion 2a at a predetermined depth in the axial direction of the guide and a groove 2e formed on the bottom of the recess 2d for engaging an O-ring 3b.
  • An inner electrode 4 is made of conductive resin including carbon particles and formed by injection molding.
  • the inner electrode 4 is engaged in the axial hole of the guide 2 at an end portion thereof.
  • the inner electrode 4 has a flange 4a provided on the axially inner, upper end thereof to be engaged with the bottom of the recess 2d and a connecting portion 4b projecting from the flange 4a in the hollow portion 1e.
  • the end portion of the flange 4a is sealed by the O-ring 3b.
  • the connecting portion 4b has a semicircular cross section.
  • An insulator washer 5 is mounted on the connecting portion 4a and abutted on the flange 4a.
  • a rectangular printed board 7 is mounted in the hollow portion 1e and abutted on the washer 5 at an end thereof.
  • the printed circuit board 7 has an oil level detector circuit 6 mounted thereon and is secured to a flat surface of the projecting connecting portion 4b by a screw 8.
  • a pair of conductive metallic clamps 9 are mounted on the opposite corners of the printed board 7 and engaged with the inside wall of the sensor body 1. Wires 10 for a source line and a signal line are connected to the printed board 7. An annular conductive washer 11 having a bent flange is attached to the clamps 9. The bent flange of the washer 11 engages with the inside wall of the sensor body 1. Thus, the ground of the printed board 7 is electrically connected to the sensor body 1 through the clamps 9 and washer 11.
  • An insulation cap 12 is engaged in the sensor body 1.
  • the space between the washers 5 and 11 surrounding the printed board 7 is filled with epoxiresin.
  • FIG. 4 shows the oil level detector circuit 6 mounted on the printed board 7.
  • the circuit 6 has a comparator OP and a voltage divider comprising resistors R1, R2 and a thermistor RTh connected in series between a source V (for example, +5V) in a source circuit 14 of an engine control unit 13 and the ground.
  • the inner electrode 4 of the oil sensor A is connected to the source V through a resistor R3.
  • An inverting terminal of the comparator OP is connected between the resistors R1 and R2 and a non-inverting terminal is connected between the electrode 4 and the resistor R3.
  • Resistances 5 of the resistors R1, R2 and R3 and the thermistor RTh are determined such that the potentials satisfy Va ⁇ Vb when oil exists between the sensor body 1 and the inner electrode 4.
  • the resistance of oil reduces with an increase of temperature of the oil.
  • the thermistor RTh is arranged to have a negative characteristic RTh which coincides with the variation of the resistance, so that the relation of the voltages Va and Vb may be Va ⁇ Vb.
  • the comparator OP When the oil resistance between the electrodes is detected, the comparator OP produces a low level signal from an output terminal thereof.
  • the comparator OP produces a high level signal.
  • the output terminal of the comparator OP is connected to the engine control unit 13 through wires 10 and a connector 17 as shown in FIG. 1.
  • the engine control unit 13 is provided with the source circuit 14, an auxiliary timer 15 and an engine stopping circuit 16.
  • the auxiliary timer 15 is provided for preventing an erroneous detection caused by the movement of the surface of oil.
  • the auxiliary timer 15 operates to measure a generating time of the high level signal. If the generating time exceeds a predetermined time, the timer 15 produces a trigger signal which is applied to the engine stopping circuit 16.
  • the engine stopping circuit 16 operates to ground a primary winding of an ignition coil (not shown) of a gasoline engine or to position a control rack of a fuel injection pump of a diesel engine to a close position. Thus, the engine stops and an alarm lamp 18 of a light emitting diode is turned on.
  • the oil sensor A is inserted into the threaded opening 19a of the oil pan 19 and the outer thread 1c of the sensor body 1 is screwed in the threaded opening 19a, interposing the packing 20.
  • the oil level sensor A is attached to the oil pan 19.
  • both the lower portions of the sensor body 1 and the inner electrode 4 are soaked in the oil of the oil pan 19.
  • the sensor detects the resistance of oil between the sensor body 1 and the inner electrode 4.
  • potentials Va and Vb between the points a and b are Va ⁇ Vb.
  • the comparator OP produces a low level signal.
  • the oil level detector circuit 6 is mounted in the oil level sensor A, and hence the low and high level signals are directly applied to the engine control unit without a shielded wire. Accordingly, the oil level detecting system becomes simple in construction, thereby reducing the manufacturing cost of the system.
  • the oil level sensor A produces a signal having a high or low level in accordance with the oil level, the process in the control unit 13 becomes simple and a system for preventing noise is simplified.
  • the oil level sensor can be easily used for various types of the control circuits.
  • the sensor body 1 is made of conductive resin including carbon, the resistance of the sensor body is very small compared with the oil resistance. Accordingly, the resistance of the sensor body has a value within a detecting error of the sensor.
  • the sensor body 1 and the inner electrode 4 are made of resin having a low heat conductivity, the heat of the oil and the heat of the crankcase of the engine are hardly transmitted to the oil level detector circuit 6 in the oil level sensor A. Thus, the deterioration of the detector 6 caused by heat is eliminated.
  • the level of the oil in the oil pan is accurately detected without the influence of noise.
  • the number of parts of the oil level sensor are reduced, thereby reducing manufacturing cost.
  • an oil level sensor having a high reliability and operability is provided.

Landscapes

  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Fluid Mechanics (AREA)
  • General Physics & Mathematics (AREA)
  • Lubrication Details And Ventilation Of Internal Combustion Engines (AREA)
  • Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)
  • Geophysics And Detection Of Objects (AREA)

Abstract

An oil level sensor has a cylindrical hollow sensor body and an elongated inner electrode provided in the sensor body at a distance from the inner wall of the sensor body. The sensor body and the inner electrode are made of conductive resin including carbon particles. An oil level detector circuit is provided in the sensor body.

Description

BACKGROUND OF THE INVENTION
The present invention relates to an oil level sensor for detecting the level of lubricating oil in an internal combustion engine.
In an industrial engine, if the engine is operated without noticing a shortage of the lubricating oil, the engine becomes damaged due to burning.
Consequently, an oil level sensor is provided for monitoring the level of the lubricating oil at all times. When the oil sensor detects a lower level for the oil lower than a set level, the engine is stopped or an alarm lamp is turned on to prevent the engine from being damaged.
Japanese Patent Applications Laid-Open 62-93417 and 62-26379 disclose oil sensors employed with an oil pressure switch and a reed switch, respectively.
The oil sensor employed with the reed switch consists of various components such as a float and a magnet in addition to the reed switch, so that the oil sensor is complicated in construction. Further, the sensor must be assembled in a crankcase before assembling the engine.
The oil sensor employed with the oil pressure switch can not be used for an engine without an oil pump.
To the contrary, a fluid sensor detects the amount of fluid by measuring a resistance of the fluid.
The fluid sensor comprises a center electrode and an outer electrode surrounding the center electrode at a predetermined distance. The fluid sensor detects the volume and concentration of the fluid, and other conditions in accordance with the variation of the resistance between the center electrode and the outer electrode.
The variation of the resistance is detected by measuring a current flowing in the fluid sensor. However, the current representing the variation of the resistance of oil is very small, because the resistance is large. Thus, a shielded wire must be employed for a signal line in order to prevent the influence of noises. However, it is difficult to completely eliminate the influence of noise.
Further, the shielded wire must be connected to a control unit by a connector, which causes an increase of parts and the assembling process.
Moreover, a high-insulating resistor must be provided in the control unit. However, the high-insulating resistor electrically affects other circuits.
SUMMARY OF THE INVENTION
The object of the present invention is to provide an oil level sensor which detects the level of oil in an oil pan with accuracy without influence of noise.
Another object of the present invention is to provide an oil level sensor in which the number of the parts of the sensor is reduced, thereby reducing the manufacturing cost and the assembling process.
According to the present invention, there is provided an oil level sensor comprising a cylindrical hollow sensor body made of conductive resin, an inner electrode guide made of an insulator and secured to an inner wall of the sensor body, an elongated inner electrode made of conductive resin and securely mounted in the inner electrode guide so as to keep a predetermined distance from the inner wall of the sensor body, and an oil level detector circuit provided in the sensor body and electrically connected between the inner electrode and the sensor body.
In an aspect of the invention, the inner electrode has a flange at a base portion thereof and a connecting portion projected from the flange, and a circuit board is secured to the connecting portion. An oil level detector circuit has a comparator for producing an output signal having a logical level and a thermistor for compensating the resistance variation of oil caused by heat.
The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic illustration of an oil level sensor according to the present invention, a part of which is shown in section;
FIG. 2 is a sectional view showing the oil level sensor;
FIG. 3 is a sectional view of the oil level sensor taken along the line III--III of FIG. 2;
FIG. 4 is a circuit of an oil level detector; and
FIG. 5 is a graph showing characteristic of insulation resistance and temperature of oil.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1, an oil level sensor A is provided in an oil pan 19 of an engine (not shown) by engaging a threaded opening 19a formed in the oil pan through a packing 20.
Referring to FIGS. 2 and 3, the oil sensor A has a cylindrical sensor body 1 served as an outer electrode, which is made of electrically conductive resin including carbon particles molded by injection molding.
The sensor body 1 comprises a screw head 1a, a flange 1b adjacent to the screw head 1a, and an outer thread 1c adjacent to the flange 1b. The sensor body 1 has a cylindrical hollow portion 1e and air vents 1f formed in the body, communicating with the hollow portion 1e. A stepwise portion 1g is formed on an inside wall of the sensor body 1.
In the hollow portion 1e, an inner electrode guide 2 is securely mounted. The guide 2 is made of high-resistance insulation resin with heat proof. The guide 2 has a shoulder portion 2a engaged with the stepwise portion 1g of the sensor body 1, a cylindrical body portion 2a' and a taper portion 2c formed on an end of the cylindrical portion 2a'. The guide 2 has an axial hole formed along the axis, opening at both ends. An annular groove 2b is formed on the cylindrical body portion 2a' for engaging an O-ring 3a.
The entire outer surface of the guide 2 or at least an outer surface of the taper portion 2c is coated with such material as fluororesin having heat proof, electrical resistivity and oil repelling characteristics for preventing the oil from adhering to the guide 2.
The guide 2 has a recess 2d formed on the shoulder portion 2a at a predetermined depth in the axial direction of the guide and a groove 2e formed on the bottom of the recess 2d for engaging an O-ring 3b.
An inner electrode 4 is made of conductive resin including carbon particles and formed by injection molding. The inner electrode 4 is engaged in the axial hole of the guide 2 at an end portion thereof. The inner electrode 4 has a flange 4a provided on the axially inner, upper end thereof to be engaged with the bottom of the recess 2d and a connecting portion 4b projecting from the flange 4a in the hollow portion 1e. The end portion of the flange 4a is sealed by the O-ring 3b. The connecting portion 4b has a semicircular cross section. An insulator washer 5 is mounted on the connecting portion 4a and abutted on the flange 4a. A rectangular printed board 7 is mounted in the hollow portion 1e and abutted on the washer 5 at an end thereof. The printed circuit board 7 has an oil level detector circuit 6 mounted thereon and is secured to a flat surface of the projecting connecting portion 4b by a screw 8.
A pair of conductive metallic clamps 9 are mounted on the opposite corners of the printed board 7 and engaged with the inside wall of the sensor body 1. Wires 10 for a source line and a signal line are connected to the printed board 7. An annular conductive washer 11 having a bent flange is attached to the clamps 9. The bent flange of the washer 11 engages with the inside wall of the sensor body 1. Thus, the ground of the printed board 7 is electrically connected to the sensor body 1 through the clamps 9 and washer 11.
An insulation cap 12 is engaged in the sensor body 1. The space between the washers 5 and 11 surrounding the printed board 7 is filled with epoxiresin.
FIG. 4 shows the oil level detector circuit 6 mounted on the printed board 7. The circuit 6 has a comparator OP and a voltage divider comprising resistors R1, R2 and a thermistor RTh connected in series between a source V (for example, +5V) in a source circuit 14 of an engine control unit 13 and the ground. The inner electrode 4 of the oil sensor A is connected to the source V through a resistor R3. An inverting terminal of the comparator OP is connected between the resistors R1 and R2 and a non-inverting terminal is connected between the electrode 4 and the resistor R3.
If the resistance between the sensor body 1 and the inner electrode 4 is RDUT, potential Va at a point a is represented as ##EQU1## and potential Vb at a point b is ##EQU2##
Resistances 5 of the resistors R1, R2 and R3 and the thermistor RTh are determined such that the potentials satisfy Va<Vb when oil exists between the sensor body 1 and the inner electrode 4.
As shown in FIG. 5, the resistance of oil reduces with an increase of temperature of the oil. The thermistor RTh is arranged to have a negative characteristic RTh which coincides with the variation of the resistance, so that the relation of the voltages Va and Vb may be Va<Vb.
When the oil resistance between the electrodes is detected, the comparator OP produces a low level signal from an output terminal thereof.
If the level of the oil in the oil pan 19 lowers to expose the sensor body 1 from the oil, the resistance RDOU between the sensor body 1 and the inner electrode 4 becomes large. Consequently, the potential Va becomes higher than Vb (Va>Vb). Thus, the comparator OP produces a high level signal.
The output terminal of the comparator OP is connected to the engine control unit 13 through wires 10 and a connector 17 as shown in FIG. 1. The engine control unit 13 is provided with the source circuit 14, an auxiliary timer 15 and an engine stopping circuit 16.
The auxiliary timer 15 is provided for preventing an erroneous detection caused by the movement of the surface of oil. When the high level signal is applied from the detector circuit 6 to the unit 13, the auxiliary timer 15 operates to measure a generating time of the high level signal. If the generating time exceeds a predetermined time, the timer 15 produces a trigger signal which is applied to the engine stopping circuit 16.
The engine stopping circuit 16 operates to ground a primary winding of an ignition coil (not shown) of a gasoline engine or to position a control rack of a fuel injection pump of a diesel engine to a close position. Thus, the engine stops and an alarm lamp 18 of a light emitting diode is turned on.
As shown in FIG. 1, the oil sensor A is inserted into the threaded opening 19a of the oil pan 19 and the outer thread 1c of the sensor body 1 is screwed in the threaded opening 19a, interposing the packing 20. Thus, the oil level sensor A is attached to the oil pan 19.
Describing the operation, when a key switch (not shown) of the engine is turned on to start the engine, a battery voltage is applied to the control unit 13 and the constant voltage V is applied to the oil level detector circuit 6 in the oil level sensor A.
During the operation of the engine, if the oil pan 11 is sufficiently filled with the oil, both the lower portions of the sensor body 1 and the inner electrode 4 are soaked in the oil of the oil pan 19. The sensor detects the resistance of oil between the sensor body 1 and the inner electrode 4. As hereinbefore described, potentials Va and Vb between the points a and b are Va<Vb. The comparator OP produces a low level signal.
If the level of the oil in the oil pan 19 lowers to expose the sensor body 1 from the oil, the resistance between the sensor body 1 and the inner electrode becomes large. The potential Va applied to the non-inverting terminal of the comparator OP becomes higher than the potential Vb applied to the inverting terminal. The comparator OP produces accordingly a high level signal.
In accordance with the present invention, the oil level detector circuit 6 is mounted in the oil level sensor A, and hence the low and high level signals are directly applied to the engine control unit without a shielded wire. Accordingly, the oil level detecting system becomes simple in construction, thereby reducing the manufacturing cost of the system.
Since the oil level sensor A produces a signal having a high or low level in accordance with the oil level, the process in the control unit 13 becomes simple and a system for preventing noise is simplified. The oil level sensor can be easily used for various types of the control circuits.
Since the sensor body 1 is made of conductive resin including carbon, the resistance of the sensor body is very small compared with the oil resistance. Accordingly, the resistance of the sensor body has a value within a detecting error of the sensor.
Since the sensor body 1 and the inner electrode 4 are made of resin having a low heat conductivity, the heat of the oil and the heat of the crankcase of the engine are hardly transmitted to the oil level detector circuit 6 in the oil level sensor A. Thus, the deterioration of the detector 6 caused by heat is eliminated.
If the vertical position of the oil sensor A is set at a higher position, the shortage of oil is indicated without stopping the engine.
The level of the oil in the oil pan is accurately detected without the influence of noise. The number of parts of the oil level sensor are reduced, thereby reducing manufacturing cost. Thus, an oil level sensor having a high reliability and operability is provided.
While the presently preferred embodiments of the present invention have been shown and described, it is to be understood that these disclosures are for the purpose of illustration and that various changes and modifications may be made without departing from the scope of the invention as set forth in the appended claims.

Claims (7)

What is claimed is:
1. An oil level sensor for sensing a level of oil in an oil pan, comprising:
a cylindrical sensor body having a cylindrical hollow portion, said cylindrical sensor body being made of electrically conductive resin having low heat conductivity including carbon;
an elongated inner electrode made of electrically conductive resin having low heat conductivity;
an inner electrode guide made of an insulator and supporting said elongated inner electrode so as to provide a predetermined space between an inner surface of said cylindrical sensor body and said inner electrode; and
an oil level detecting circuit electrically connected to the inner electrode and the sensor body for detecting resistance between said sensor body and said inner electrode and for producing a logical level signal when said predetermined space is filled with the oil.
2. The oil level sensor according to claim 1, wherein
said inner electrode has a flange and a connecting portion projecting from said flange, and a circuit board is secured to the connecting portion, said oil level detecting circuit is provided on said circuit board.
3. The oil level sensor according to claim 1, wherein
said oil level detecting circuit comprises
a predetermined resistance, and
comparing means for comparing said predetermined resistance with said first-mentioned resistance between said sensor body and said inner electrode, and for producing an output signal having a logical level so as to detect the level of the oil with accuracy without influence of noise.
4. The oil level sensor according to claim 1, wherein
said oil level detecting circuit has a thermistor for compensating resistance variation of the oil caused by variation in temperature of the oil.
5. The oil level sensor according to claim 1, wherein
said carbon is in the form of carbon particles.
6. The oil level sensor according to claim 1, wherein
said inner electrode is further made of carbon.
7. The oil level sensor according to claim 6, wherein
said carbon of said inner electrode is in the form of carbon particles.
US07/528,036 1989-05-25 1990-05-23 Oil level sensor for an internal combustion engine Expired - Lifetime US5046583A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP1132089A JP2731240B2 (en) 1989-05-25 1989-05-25 Oil sensor
JP1-132089 1989-05-25

Publications (1)

Publication Number Publication Date
US5046583A true US5046583A (en) 1991-09-10

Family

ID=15073238

Family Applications (1)

Application Number Title Priority Date Filing Date
US07/528,036 Expired - Lifetime US5046583A (en) 1989-05-25 1990-05-23 Oil level sensor for an internal combustion engine

Country Status (4)

Country Link
US (1) US5046583A (en)
EP (1) EP0399824B1 (en)
JP (1) JP2731240B2 (en)
DE (1) DE69015439T2 (en)

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5532527A (en) * 1992-05-06 1996-07-02 Zatler; Andrej Level switch
US5687687A (en) * 1995-06-07 1997-11-18 Cummins Engine Company, Inc. Oil level sensor system
WO2002024482A1 (en) * 2000-09-22 2002-03-28 Detroit Diesel Corporation Maintenance alert system for heavy-duty trucks
US6374949B2 (en) * 1998-12-28 2002-04-23 Renk Aktiengesellschaft Transmission
US20050097952A1 (en) * 2003-11-12 2005-05-12 Steph James C. Conductive sensor for fluid level sensing
US20070057675A1 (en) * 2005-09-09 2007-03-15 Honda Motor Co., Ltd. Oil sensor mounting structure
CN100337097C (en) * 2003-10-23 2007-09-12 松下电器产业株式会社 Apparatus for testing electrode
USRE39845E1 (en) 1999-03-22 2007-09-18 Detroit Diesel Corporation Maintenance alert system for heavy-duty trucks
US20080053217A1 (en) * 2006-08-31 2008-03-06 Honda Motor Co., Ltd. Oil level detection system of internal combustion engine
US20080247912A1 (en) * 2003-09-11 2008-10-09 Kenjiro Izutani Urea Concentration Identification Device for Urea Solution
US20100007360A1 (en) * 2007-06-06 2010-01-14 Udo Kaess Fluid sensor device
US20100175471A1 (en) * 2009-01-09 2010-07-15 Dennis Jr Paul G Robust oil level sensor
US20130139643A1 (en) * 2011-12-06 2013-06-06 Dennis Reid Transmission and transmission housing with multiple dipsticks and dipstick apertures, circumferentially positioned internal lugs and an adjacent fluid inlet port
US20140116808A1 (en) * 2012-11-01 2014-05-01 Ronald J. Kile Lubricating oil monitoring and maintenance cap with oil level monitoring system
US20160084695A1 (en) * 2014-09-23 2016-03-24 Caterpillar Inc. System and method of monitoring oil level in transmission system of machine
CN108119193A (en) * 2016-11-28 2018-06-05 赛峰航空器发动机 Include the fuel tank of oil level control device
US20240060436A1 (en) * 2020-12-30 2024-02-22 Hd Hyundai Infracore Co., Ltd. Oil level sensor cover and engine comprising same

Families Citing this family (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5053745A (en) * 1989-06-26 1991-10-01 Fuji Jukogyo Kabushiki Kaisha Apparatus for warning of engine oil abnormality
GB9025948D0 (en) * 1990-11-29 1991-01-16 British Gas Plc Measuring probe
DE4116355C2 (en) * 1991-05-18 2000-05-18 Wilo Gmbh Sensor
FR2766268B1 (en) * 1997-07-21 1999-10-08 Aerospatiale WATER DETECTOR AND SUBMARINE AMMUNITION PROVIDED WITH SUCH A DETECTOR
DE19757065A1 (en) * 1997-12-20 1999-06-24 Bayerische Motoren Werke Ag Oil level sensor
JP2007504453A (en) * 2003-09-04 2007-03-01 コンチネンタル・テベス・アーゲー・ウント・コンパニー・オーハーゲー Measuring device for measuring liquid properties in a vehicle
DE102006005529B4 (en) * 2006-02-07 2016-02-11 Röchling Automotive AG & Co. KG Plastic container with at least one electrode made of electrically conductive plastic
FR2906364B1 (en) * 2006-09-27 2008-11-21 Peugeot Citroen Automobiles Sa SYSTEM FOR MOUNTING A DEVICE FOR MEASURING THE LEVEL AND TEMPERATURE OF OIL
EP2886024B1 (en) * 2013-12-18 2019-02-20 ELECTROLUX PROFESSIONAL S.p.A. Improved detection assembly for electric appliances
JP6993679B2 (en) * 2017-11-22 2022-01-13 センスプロ株式会社 Lubricating oil sensor head and sensor system

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3593270A (en) * 1967-07-10 1971-07-13 Richard E Walker Liquid level sensing and indicating system
US3701138A (en) * 1971-03-25 1972-10-24 Data Eng Inc Fluid level sensor and system
US4135186A (en) * 1977-02-23 1979-01-16 Hitachi, Ltd. Liquid level detecting apparatus
US4638288A (en) * 1982-03-22 1987-01-20 Remec Matthew J Thermal level detector for conductive or nonconductive liquids or gases
JPS6226379A (en) * 1985-07-29 1987-02-04 Kawasaki Heavy Ind Ltd Automatic engine stopper
JPS6293417A (en) * 1985-10-21 1987-04-28 Honda Motor Co Ltd Engine oil level detecting method
US4745893A (en) * 1986-12-03 1988-05-24 Caterpillar Inc. Digital oil level sensor
US4755790A (en) * 1984-07-04 1988-07-05 Suzuki Jidosha Kogyo Kabushiki Kaisha Float switch, a control apparatus and a warning apparatus of an engine

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE818060C (en) * 1950-05-18 1951-10-22 Karl Ziegler Device for switching off an electrical power consuming device depending on the level of the level of a liquid
DE2339481C3 (en) * 1973-08-03 1979-12-06 Siemens Ag, 1000 Berlin Und 8000 Muenchen Electric probe for use in electrically conductive liquids
US4322713A (en) * 1980-03-10 1982-03-30 Duck Sherman W Level monitoring methods and apparatus particularly for high-resistivity liquids
DE3344879A1 (en) * 1983-12-12 1985-06-13 Lothar 2940 Wilhelmshaven Sabrowsky Level-limiting value transmitter for liquid containers or the like
JPH0424417Y2 (en) * 1986-01-10 1992-06-09
JPS62115631U (en) * 1986-01-13 1987-07-23
US4806847A (en) * 1986-12-09 1989-02-21 Caterpillar Inc. Dielectric liquid level sensor and method
JPS63101815U (en) * 1986-12-20 1988-07-02
JPS63155026U (en) * 1987-03-31 1988-10-12

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3593270A (en) * 1967-07-10 1971-07-13 Richard E Walker Liquid level sensing and indicating system
US3701138A (en) * 1971-03-25 1972-10-24 Data Eng Inc Fluid level sensor and system
US4135186A (en) * 1977-02-23 1979-01-16 Hitachi, Ltd. Liquid level detecting apparatus
US4638288A (en) * 1982-03-22 1987-01-20 Remec Matthew J Thermal level detector for conductive or nonconductive liquids or gases
US4755790A (en) * 1984-07-04 1988-07-05 Suzuki Jidosha Kogyo Kabushiki Kaisha Float switch, a control apparatus and a warning apparatus of an engine
JPS6226379A (en) * 1985-07-29 1987-02-04 Kawasaki Heavy Ind Ltd Automatic engine stopper
JPS6293417A (en) * 1985-10-21 1987-04-28 Honda Motor Co Ltd Engine oil level detecting method
US4745893A (en) * 1986-12-03 1988-05-24 Caterpillar Inc. Digital oil level sensor

Cited By (32)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5532527A (en) * 1992-05-06 1996-07-02 Zatler; Andrej Level switch
US5687687A (en) * 1995-06-07 1997-11-18 Cummins Engine Company, Inc. Oil level sensor system
US6374949B2 (en) * 1998-12-28 2002-04-23 Renk Aktiengesellschaft Transmission
USRE39845E1 (en) 1999-03-22 2007-09-18 Detroit Diesel Corporation Maintenance alert system for heavy-duty trucks
WO2002024482A1 (en) * 2000-09-22 2002-03-28 Detroit Diesel Corporation Maintenance alert system for heavy-duty trucks
US7829024B2 (en) * 2003-09-11 2010-11-09 Mitsui Mining & Smelting Co., Ltd. Urea concentration identification device for urea solution
US20080247912A1 (en) * 2003-09-11 2008-10-09 Kenjiro Izutani Urea Concentration Identification Device for Urea Solution
CN100337097C (en) * 2003-10-23 2007-09-12 松下电器产业株式会社 Apparatus for testing electrode
US20050097952A1 (en) * 2003-11-12 2005-05-12 Steph James C. Conductive sensor for fluid level sensing
WO2005047827A3 (en) * 2003-11-12 2006-01-26 Stemco Llc Conductive sensor for fluid level sensing
WO2005047827A2 (en) * 2003-11-12 2005-05-26 Stemco Llc Conductive sensor for fluid level sensing
US7263964B2 (en) * 2005-09-09 2007-09-04 Honda Motor Co., Ltd. Oil sensor mounting structure
US20070057675A1 (en) * 2005-09-09 2007-03-15 Honda Motor Co., Ltd. Oil sensor mounting structure
US20080053217A1 (en) * 2006-08-31 2008-03-06 Honda Motor Co., Ltd. Oil level detection system of internal combustion engine
US20100007360A1 (en) * 2007-06-06 2010-01-14 Udo Kaess Fluid sensor device
US20100175471A1 (en) * 2009-01-09 2010-07-15 Dennis Jr Paul G Robust oil level sensor
US9297685B2 (en) 2009-01-09 2016-03-29 Hamilton Sundstrand Corporation Robust oil level sensor
US20130139643A1 (en) * 2011-12-06 2013-06-06 Dennis Reid Transmission and transmission housing with multiple dipsticks and dipstick apertures, circumferentially positioned internal lugs and an adjacent fluid inlet port
US8789443B2 (en) * 2011-12-06 2014-07-29 Dennis Reid Transmission and transmission housing with multiple dipsticks and dipstick apertures, circumferentially positioned internal lugs and an adjacent fluid inlet port
US9657898B1 (en) 2012-11-01 2017-05-23 Ronald J. Kile Lubricating oil monitoring and maintenance cap with oil level monitoring system
US20140116808A1 (en) * 2012-11-01 2014-05-01 Ronald J. Kile Lubricating oil monitoring and maintenance cap with oil level monitoring system
US9458965B2 (en) * 2012-11-01 2016-10-04 Ronald J. Kile Lubricating oil monitoring and maintenance cap with oil level monitoring system
US20150136527A1 (en) * 2012-11-01 2015-05-21 Ronald J. Kile Lubricating oil monitoring and maintenance cap with oil level monitoring system
US10215334B1 (en) * 2012-11-01 2019-02-26 Ronald J. Kile Lubricating oil monitoring and maintenance cap with oil level monitoring system
US20160084695A1 (en) * 2014-09-23 2016-03-24 Caterpillar Inc. System and method of monitoring oil level in transmission system of machine
US9593974B2 (en) * 2014-09-23 2017-03-14 Caterpillar Inc. System and method of monitoring oil level in transmission system of machine
CN108119193A (en) * 2016-11-28 2018-06-05 赛峰航空器发动机 Include the fuel tank of oil level control device
US20180156066A1 (en) * 2016-11-28 2018-06-07 Safran Aircraft Engines Oil tank comprising an oil level control device
US10683774B2 (en) * 2016-11-28 2020-06-16 Safran Aircraft Engines Oil tank comprising an oil level control device
CN108119193B (en) * 2016-11-28 2022-03-18 赛峰航空器发动机 Oil tank comprising oil level control device
US20240060436A1 (en) * 2020-12-30 2024-02-22 Hd Hyundai Infracore Co., Ltd. Oil level sensor cover and engine comprising same
US12012879B2 (en) * 2020-12-30 2024-06-18 Hd Hyundai Infracore Co., Ltd. Oil level sensor cover and engine comprising same

Also Published As

Publication number Publication date
DE69015439T2 (en) 1995-05-04
EP0399824A2 (en) 1990-11-28
EP0399824B1 (en) 1994-12-28
JPH02310428A (en) 1990-12-26
DE69015439D1 (en) 1995-02-09
EP0399824A3 (en) 1991-03-27
JP2731240B2 (en) 1998-03-25

Similar Documents

Publication Publication Date Title
US5046583A (en) Oil level sensor for an internal combustion engine
EP0399686B1 (en) An electrical resistance oil level sensor for an internal combustion engine
US7151383B2 (en) Oil condition sensor
US4806847A (en) Dielectric liquid level sensor and method
EP0101580B1 (en) Capacitance-type material level indicator
JP2554296B2 (en) Device for detecting the alcohol content or calorific value of a mixture
US4135186A (en) Liquid level detecting apparatus
US5097703A (en) Capacitive probe for use in a system for remotely measuring the level of fluids
US4745893A (en) Digital oil level sensor
US4499640A (en) Method of manufacturing capacitance-type material level indicator probe
US4453124A (en) Linear inductive transducers
US3922658A (en) Fluid level monitor
US20130031963A1 (en) Water in fuel sensor
US4316174A (en) Threshold detector for a condition indication
US4801926A (en) Device for sensing the level of a liquid within the interior of a container
US6237411B1 (en) Limit-level sensor and method of determining the undershooting or overshooting of an intended level of liquid in a container
US6874481B2 (en) Fuel supply apparatus and residual fuel amount indication device for fuel supply apparatus
US4121457A (en) Liquid sensor
JP2006214997A (en) Vehicular capacitive sensor
US5150606A (en) Acceleration detector
US4945755A (en) Acceleration detector with parallel ground paths
US5461315A (en) High voltage transformer for the continuous monitoring of high voltage characteristics in a combustion engine
JPH0326425Y2 (en)
JPH0416913Y2 (en)
JPH059798Y2 (en)

Legal Events

Date Code Title Description
AS Assignment

Owner name: FUJI JUKOGYO KABUSHIKI KAISHA, 7-2 NISHISHINJUKU 1

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNORS:SASAKI, ASAO;KUBOTA, YOSUKE;REEL/FRAME:005347/0814

Effective date: 19900508

STCF Information on status: patent grant

Free format text: PATENTED CASE

FPAY Fee payment

Year of fee payment: 4

FPAY Fee payment

Year of fee payment: 8

FPAY Fee payment

Year of fee payment: 12